http://platform.dukascopy.com/demo_3/jforex_3.jnlp how is work not open?
A .jnlp file won't open if you don't have Java installed.
The recommended way is to use JForex Platform installer, which comes bundled with Java, enables easier and faster setup and access, and more.
https://www.dukascopy.com/swiss/english/forex/dealstation/